Search results

A 70 MHz Moxon rectangle antenna, built with 0.83mm enamelled copper wire and a lightweight fiberglass kite spar frame, offers a compact two-element beam solution for the 4-meter band. This design, originally for HF, scales effectively to VHF, reducing the antenna's width to approximately 75% of a half-wavelength while allowing direct coaxial cable feeding. The author, G6GVI, details the construction process, including the use of an automated design tool for precise dimensions. Initial field testing revealed a VSWR of approximately 1.3, with distinct nulls observed at 90 degrees when the antenna was mounted horizontally. The lightweight build, supported by a wooden block and U-bolt for mast attachment, makes it suitable for thinner mast sections. Further experimentation included testing with vertical polarization and considering its potential for indoor loft installation due to its relatively short major axis, offering a discreet option for urban hams.

Examines the practical considerations and technical challenges of deploying mobile antennas for 10-meter operation, particularly for operators on the move. It addresses the inherently _lossy_ nature of shortened, loaded vertical antennas typically used in mobile configurations, encouraging hams to view these limitations as engineering challenges. The resource provides actionable advice on safeguarding vehicle electronics, selecting appropriate cabling like _RG-213_, and properly grounding antenna mounts to the vehicle chassis. Specific mounting strategies are detailed, including roof, trunk lip, and side-mounting for trucks and vans, along with their respective advantages and drawbacks. It emphasizes the importance of a robust ground plane and suggests methods for improving grounding beyond simple set screws. The article also touches on antenna choices, mentioning "bugcatchers" and "Hamstick types" as viable options for 10 meters. Furthermore, the guide transitions to stationary mobile operation, where antenna options expand significantly. It outlines how to deploy portable dipoles or 2-element beams from a parked vehicle, offering practical tips for assembly, storage, and mast guying using simple materials like a concrete block. It notes that a 5/8 wavelength height, approximately **20 feet** on 10 meters, often yields good short-skip and DX performance, even with a take-off angle above **20 degrees**.

Over 45 years of amateur radio experience inform the homebrew projects detailed on this personal website, with a particular focus on microwave frequencies. The site showcases a 24 GHz transverter and a more recent 47 GHz transverter, demonstrating practical construction techniques for extreme high-frequency operation. These projects often involve custom circuit design and careful component selection to achieve stable performance at millimeter-wave bands. Key projects include a _harmonic converter_ for frequency measurement and a tracking spectrum analyzer, essential tools for microwave experimenters. The site also documents a CW sidetone generator and a TX/RX sequencer, illustrating fundamental building blocks for radio equipment. Details on a digital frequency meter and an S-meter/dBm meter provide insights into test equipment construction. Specific achievements, such as a **24 GHz** tropo QSO with DK3SE in 2021, highlight the operational success of these homebrewed systems. The content reflects a long-standing dedication to self-sufficiency in amateur radio, providing practical examples for those interested in building their own gear.

If you have ever tried transmitting on HF from a tall block of apartments, where it's just not possible to erect a substantial aerial system, then this article is for you

Demonstrates the construction of a **homebrew spectrum analyzer** designed by Wes Hayward, W7ZOI, and Terry White, K7TAU, enabling radio amateurs to build a capable test instrument without significant expense. The resource details a _double-conversion superheterodyne_ circuit, employing intermediate frequencies of 110 MHz and 10 MHz, and covers essential blocks such as the time base, logarithmic amplifier, resolution filters, and local oscillators. It highlights the use of hybrid and monolithic ICs, including mixers, amplifiers, and VCOs, to simplify construction while maintaining performance. The design supports useful measurements in the 50 kHz to 70 MHz range, with methods outlined for extending capabilities into VHF and UHF. The authors emphasize that this analyzer, while simple to build, is intended for serious measurements, requiring careful control of signal levels to avoid spurious responses. It uses an oscilloscope for display, with specific instructions for calibration and adjustment of various stages, including the log amplifier and IF gain. The guide provides detailed schematics and component lists for each section, such as the 110 MHz triple-tuned band-pass filter, which achieved **90 dB** image rejection, a significant improvement over double-tuned circuits. Practical advice on alignment and troubleshooting is included, drawing on the authors' extensive experience in RF circuit design.

This resource presents over 100 Q-signals, each with its corresponding question and answer format, as standardized by the International Telecommunication Union. The content delineates how these abbreviations can be expanded with additional groups, call signs, place names, or numerical data to provide specific context. It clarifies that a question mark following an abbreviation or its complementary information transforms it into a query. The document highlights that these operating signals, or Op Sigs, are prescribed for international use across all communication types, including military and non-military applications. It references their inclusion in Appendix 9 to the Radio Regulations Annex of the International Telecommunications Convention (Atlantic City) 1947 for QRA to QUZ blocks, and ICAO publications Dec 6100-COM/504/1 for QAA to QNZ blocks. The page specifically marks Q-signals of particular interest to amateur radio operators in red. The utility of Q-signals for concise communication in radiotelegraphy is evident, providing a structured method for conveying complex information efficiently. The resource serves as a practical reference for operators needing to quickly interpret or formulate messages using standardized codes, particularly beneficial for CW operation and international contacts.

Terrasat Communications specializes in advanced RF technology for satellite communication, focusing on _Intelligent Block Up Converters_ (IBUCs) and Solid State Power Amplifiers (SSPAs). These products are engineered to enhance satellite link performance, offering features like extended frequency ranges and high power efficiency. The IBUC series, for instance, integrates a BUC with an SSPA, enabling operators to install, configure, and monitor units for both commercial and military satellite applications, ensuring reliable, high-performance connectivity worldwide. The company's offerings support various satellite bands, including C, X, Ku, and Ka, providing solutions for diverse operational requirements. Their technology is designed for robust field performance, with products like the _IBUC2_ and _IBUCG_ models demonstrating the integration of advanced diagnostics and control capabilities, which are crucial for maintaining optimal signal integrity in demanding environments. Terrasat's focus on _SSPA_ technology underscores a commitment to power efficiency and compact design.

MorseMaker is an up-to-date replacement for the Morse Machine shown further down this page. It has been re-written using a different programming language and is now entirely 'stand-alone' requiring no run-time support files. This version also works with Windows XP and can use the soundcard but please note that, unlike its predecessor, it does not split the alphabet into smaller 'learning' blocks and does not incorporate the Morse reader.

Presents the official service manual for the **Kenwood TL-922** and **TL-922A** HF linear amplifiers, offering comprehensive technical documentation essential for maintenance and repair. This resource includes detailed circuit diagrams, block diagrams, parts lists, and alignment procedures for optimal performance. It covers critical sections such as the high-voltage power supply, RF deck, and control circuitry, providing specific values for components and test points. Operators and technicians utilize this manual to troubleshoot common issues, perform routine adjustments, and understand the intricate design of these classic tube-based amplifiers. It outlines steps for bias adjustments, neutralization, and power output calibration, ensuring the amplifier operates within specifications across the 160-10 meter amateur bands. The document also details safety precautions for working with high voltages present in the amplifier.

Applying for an FCC vanity call sign requires navigating the _Universal Licensing System_ (ULS) database to identify available call sign blocks and specific desired combinations. The process involves submitting an online application via the FCC website, ensuring all instructions are meticulously followed to avoid rejection. Typical processing time for a vanity call sign application is approximately **18 days**, after which the ULS database reflects the updated license grant. Operators often seek vanity call signs for various reasons, including aligning with a new license class, desiring a shorter call sign for CW efficiency, or simply preferring a more memorable phonetics. The resource emphasizes self-application to avoid third-party service fees, directing users to verify availability through tools like Vanity HQ. Key steps include selecting a primary call sign and several alternates, ensuring the chosen call sign conforms to FCC rules for the operator's license class. Payment can be made online or via check, with prompt submission critical to prevent application dismissal.

FPP PIC programming software

A simple RF oscillator by Harry Lythall - SM0VPO

A SSB CW transceiver for six meters band with schematic and block diagram

Radio frequency systems require robust protection against transient voltage events, which can severely damage sensitive equipment. This resource details a range of **RF surge protection** devices, including models with DC Pass, DC Block, Bias T, and Ultra Low PIM characteristics, designed to safeguard critical infrastructure. It also presents various RF filtering solutions and interconnect components, emphasizing their role in maintaining signal integrity and operational continuity across diverse applications. The site provides information on products engineered for both RF and data line protection, highlighting their utility in preventing downtime and equipment loss. Specific product categories encompass coaxial protectors, grounding items, and fiber optic solutions, indicating a broad scope of application from amateur radio installations to industrial and telecommunications networks. Furthermore, the resource mentions the availability of NOM-certified products and offers same-day shipping for many items, underscoring a commitment to rapid deployment and compliance with industry standards.

Ebook by Akira Matsuzawa Tokyo Institute of Technology, Building blocks in RF system and basic performances, Device characteristics in RF application , Low noise amplifier design, Mixer design and Oscillator design

The Yaesu VX-5R, manufactured between 199x and 200x, offers a transmit frequency range covering 50-52 MHz, 144-146 MHz, and 430-440 MHz for European models, with US versions extending to 50-54 MHz, 144-148 MHz, and 430-450 MHz. Its receiver boasts an impressive wideband capability from 0.5 MHz to 999 MHz, with cellular frequencies blocked in some regions. The unit provides up to 5 watts RF output on 6 meters and 2 meters, and 4.5 watts on 70 centimeters, with selectable lower power settings down to 300 mW. This handheld transceiver utilizes a double conversion superheterodyne receiver system, featuring a 47.25 MHz first IF for FM and 45.8 MHz for WFM. Key specifications include a frequency stability of ±5 ppm across a wide temperature range and a current drain of 25-150 mA on receive. The VX-5R supports 220 regular memory channels with alpha tags, 3 home channels, and 10 NOAA weather channels, all stored in non-volatile EEPROM. Additional features include CTCSS/PL and DCS with tone search, ARS, ARTS, an internal voltmeter, and a Spectra-Scope. The device operates on a 7.2 VDC battery pack or 10-16 VDC external power, weighing 255 grams with dimensions of 58x88x27 mm. The VX-5R was also available as the metallic silver VX-5RS.

Home Made CW paddles made from a printed circuit board and a teflon mounting block while contacts are made with simple brass threaded rods.

The Receiver Test Data resource is a detailed review database focusing on the performance metrics of various radio receivers. The methodology involves rigorous lab measurements, often adhering to standards such as the ARRL RMDR (Reciprocal Mixing Dynamic Range) and BDR (Blocking Dynamic Range). Specific test equipment and protocols are utilized to assess parameters like noise floor (dBm), AGC threshold (uV), and LO noise (dBc/Hz). For example, the _Icom IC-7300_ is evaluated with a noise floor of **-133 dBm** and an LO noise of **-141 dBc/Hz**, providing insights into its performance under different operational conditions. The resource includes a wide range of models, from the _Elecraft K3S_ to the _Yaesu FTdx-101D_, each tested for dynamic range, sensitivity, and selectivity. The data is sorted by key metrics such as third-order dynamic range and phase noise limitations, with RMDR values calculated by subtracting 27 dB from LO noise figures. This structured approach allows users to compare different receivers' capabilities, focusing on technical specifications and performance outcomes in various scenarios. DXZone Focus: Review Database | Lab Measurements | -133 dBm | ARRL RMDR

In this PDF article Zack Lau describe how to homebrew a four element yagi beam antenna for 50 MHz band, including how to build mounting blocks and tubing clamps to hold elements.

Mobile RFI, often manifesting as persistent noise in the receiver even with the antenna disconnected, frequently originates from the vehicle's power supply system. This guide details systematic troubleshooting steps, beginning with isolating the radio from the car's 12-volt supply to confirm the power system as the noise source. It emphasizes the critical importance of drawing power directly from the battery using **heavy gauge wire**, bypassing the fuse block to leverage the battery's natural capacitance for RFI suppression and ensuring a solid RF ground. Proper routing of power lines through the firewall is also covered, advocating for dedicated grommeted holes to prevent inductive coupling from other wiring harnesses. The article stresses the necessity of fusing both positive and negative leads from the battery, a crucial safety measure to prevent damage to the rig and mitigate high-current risks should the battery's engine block ground become compromised during service. Addressing **alternator whine**, a common high-pitched noise that varies with engine speed, the resource suggests checking battery connections and the alternator-to-battery harness for looseness or corrosion. It also mentions the utility of adding an external RF noise suppression capacitor in parallel with the alternator's internal capacitor for enhanced filtering, and the effectiveness of commercially available in-line power supply filters.

Supplier of RF, Microwave, & Wireless passive coaxial components, including Coaxial Attenuators, Adapters, Cables, DC Blocks, Terminations, & Connectors

Presents an alternative construction method for isolated element Yagi antennas, specifically for VHF/UHF operation. The technique utilizes commercially available vibration damping clamps (resin support blocks) to isolate 1/4-inch aluminum rod elements from a 1-inch square aluminum boom, simplifying the build process by eliminating the need for custom-machined insulators. This approach is demonstrated through the construction of 6-element Optimized Wide-Band (OWA) Yagis for the 2-meter, 1.25-meter, and 70-centimeter bands, which are well-suited for portable contesting arrays due to their light weight and decent gain. The document provides detailed specifications for element and boom materials, along with step-by-step procedures for cutting, drilling, and tapping. It also covers the fabrication of a feedpoint bracket for a direct 50-ohm SO-239 coax connection and discusses considerations for horizontal versus vertical polarization, including mast placement. The resulting 6-element models achieve an average free-space gain of 10.2 dBi and a 25 dB front-to-back ratio, with the construction technique being scalable for higher gain designs. Included are parts lists with sources, detailed mechanical drawings for each band, and EZNEC data for the 2-meter and 70-centimeter designs, showing both free-space and 30-foot elevation performance. The designs are optimized from W4RNL's original concepts using HAMCALC, ensuring good gain, passband characteristics, and front-to-back ratios for wideband Yagi operation.

Operating in the **microwave** spectrum, Response Microwave, Inc. specializes in the design and manufacturing of RF and microwave signal processing components and subsystems. The company's product line encompasses a wide array of offerings, including Connectivity Series components, rotary joints, phase shifters, cable assemblies, surge protectors, terminations, Hybridline/Couperline products, circulators/isolators, directional couplers, quadrature hybrids, attenuators, custom assemblies, filters/diplexers, DC blocks & bias tees, power dividers/combiners, laser diodes & drivers, high-frequency connectors, and precision test accessories. This extensive catalog supports various applications requiring precise signal manipulation and transmission at elevated frequencies. The resource provides access to a comprehensive product catalog and a dedicated connector catalog, detailing specifications for components like **high-frequency connectors** and test cables. While specific performance data or comparative analyses are not directly presented on the main page, the breadth of products indicates a focus on providing foundational building blocks for microwave systems. The company emphasizes customer service and aims to be a reliable source for RF/Microwave/Optics product requirements, serving a growing customer base with its specialized component offerings.

A 70 MHz Transverter project with a block diagram and schematics

Blog post announcing that Ham Radio, shortwave listeners and broadcast band listeners will be protected by Law in Europe

Appendix 42 to the Radio Regulations, published by the International Telecommunication Union (ITU), serves as the authoritative global reference for assigning call sign series to countries. This essential resource allows radio operators, including those in the amateur service, to accurately identify the national origin of a station based on its callsign prefix. It is fundamental for DXers, contesters, and anyone involved in international two-way radio communication, ensuring correct country identification for awards like _DXCC_. The table details the specific blocks of call signs allocated to each administration, facilitating the unambiguous determination of a station's geographical location. For instance, prefixes like K, W, N, and AA-AL are assigned to the United States, while G and M series denote the United Kingdom. Understanding these allocations is crucial for logging contacts and verifying QSLs. This ITU publication is regularly updated to reflect changes in national assignments and new allocations, maintaining its accuracy as the definitive source for call sign series worldwide. It underpins the global framework of radio communication.

An explanation of the different procedures and definitions that are commonly used for blocking dynamic range (BDR) measurements. Dynamic range in general is the ratio between the weakest signal a system can handle and the strongest signal the same system can handle simultaneously without an operator switching attenuators or turning volume potentiometers

Over 100 FCC districts are analyzed by this resource, providing a predictive database for amateur radio vanity callsign assignments. The system simulates the FCC's application process, calculating the probability of assignment for specific callsigns, such as KD3Q at 94% or N9QC at 97.8%. Data is meticulously organized by FCC district, detailing available, pending, and upcoming callsigns, alongside those currently blocked by renewal or other FCC administrative actions. This allows hams to gauge their chances of securing a desired callsign. The database presents specific application entries, including the date entered, receipt date, process date, the applicant's current callsign, and the vanity callsigns they have applied for. Each entry facilitates examination of predicted outcomes, which categorize potential assignments as assigned, competitive, non-assigned, unneeded, curable, or unknown status. For instance, an application for K7DM clearly shows multiple applicants, indicating a highly competitive assignment scenario. This tool is particularly useful for those seeking a **short callsign** or a **1x2, 2x1, 2x2, 1x3, 2x3, 3x1, 3x2, or 3x3 callsign** that aligns with personal preferences or contest aspirations. It provides a clear, data-driven perspective on the likelihood of obtaining a specific vanity callsign.

This multiband transverter project features power output at 13,8V 50MHz 15W, 70MHz 10W, second harmonic < 65dBc. Single N connector of antenna, suitable for a dual band Yagi. Article include Block Diagram for Dual Transverter and low pass filters

The building blocks for Amateur Radio, one concept at a time, collected since 2011 in several podcasts episodes you can listen online.

Chokes and isolation transformers are essential for receiving antennas to mitigate common mode current, which induces noise and interferes with signal quality. Common mode chokes, formed by winding feedline through ferrite cores, block unwanted current effectively. Proper selection of core material and winding turns ensures resonance near the operating frequency, reducing interference. Isolation transformers further minimize interference, crucial for multi-transmitter stations.

A UHF Frequency Counter up to 1 GHz, includes the Block Diagram , test sketch for Arduino/Genuino Nano

The article by Guy Olinger, K2AV, published in the May/June 2012 National Contest Journal, introduces the Folded Counterpoise (FCP), a compact 516-foot single-wire counterpoise elevated at 8 feet, designed for 160-meter operations on small lots like 100x150-foot backyards. Originating from efforts to revive Top Band for W0UCE on a postage-stamp property, the FCP uses strategic folds to cancel ground fields within 33 feet of center, minimizing losses to 0.13-0.53 dB—outperforming sparse or on-ground radials by up to 15 dB in poor soil—while mimicking opposed radials for efficient feedpoint impedance. Paired with a critical 1:1 or 4:1 isolation transformer (e.g., trifilar on T300-2 toroid) to block common-mode currents on coax feeds, it delivers proven results: K2AV's #8 North America low-power contest score, 7+ dB gains at W4KAZ and K5AF, and over 10,000 global web hits for DIY instructions using bare 12 AWG wire and weatherproof enclosures. Ideal for acreage-challenged hams, the FCP also excels on 80 meters with scaled dimensions, offering a low-loss alternative where full radials are impractical

This project involved designing a 7-pole Chebychev broadcast band filter to address severe interference issues caused by a new horizontal loop antenna on the KN-Q7A transceiver. The interference overwhelmed the transceiver’s front end, so a custom filter with a 3.5 MHz cutoff was built using silver mica capacitors and type 6 T130 toroidal cores. Encased in a diecast box with SO239 sockets, the filter blocks strong signals from the broadcast band, achieving over 100 dB attenuation. Tested up to 100W, it reduces interference effectively while maintaining low insertion loss across HF bands.

MeshCom 4.0 facilitates off-grid text messaging and data exchange via _LoRa_ radio modules, operating on low-power, low-cost hardware to establish networked communication capabilities. The system transmits messages, GPS positions, sensor values, and telecontrol data over significant distances with minimal power consumption. MeshCom modules can autonomously form a mesh network or integrate into a broader message network through MeshCom gateways, which ideally connect via _HAMNET_ to link disparate radio networks. Recent updates include MCMAP features, support for Lilygo T-Connect-Pro, and new firmware for T-ECHO, enhancing the system's versatility. The project provides basic specifications, detailed protocol information, and installation instructions for MeshCom 4.0, including guides for RAK WisBlock and HELTEC V3 hardware. Firmware and companion Android/iPhone applications are available for download, supporting a range of **10-20 km** line-of-sight communication.

Manufacturer of SDR Motherboards LA9310, Si5510, i.MX8MP, 4GB LPDDR4. The RFNM motherboard is a new concept, so it's worth taking a few seconds to understand it. In a nutshell, the most complicated parts are consolidated into a single block, the motherboard, and all of the interesting and fun bits are exposed via the RFNM Interface to daughterboards.

The resource provides a technical installation guide for _MeshCom 4.0_, an amateur radio mesh networking project utilizing LoRa hardware modules. It systematically covers the setup process for several supported devices, including the RAK Wireless LoRa WisBlock Core RAK4631, T-Beam T22 V1.1, T-Lora T3 V1.6.1, HELTEC WiFi ESP32 LoRa 32 (V2 and V3), HELTEC E290, ESP32 / E22 modules, and the T-deck from Lilygo. The guide specifies support for the **EU433** frequency band, ensuring amateur radio compatibility, and details the use of an online flash tool for ESP32 modules and an embedded drive for RAK modules. It further describes accessing the MeshCom 4.0 Dashboard and Map functionalities, crucial for network visualization and management. Firmware configuration for ESP32 modules is meticulously outlined, covering essential parameters such as setting callsigns, country codes, and gateway parameters via a serial console like PuTTY. Commands for activating gateway mode, setting internet IP addresses, and configuring WLAN SSID and password for modules with WLAN capability are provided, enabling modules to function as either clients or gateways within the MeshCom network.

For amateur radio operators seeking resilient, off-grid communication, the _MeshCom_ firmware provides a robust solution for text-based messaging over a mesh network. Utilizing LoRa modulation and the APRS protocol, this firmware is designed for low-energy consumption and cost-effective hardware, primarily operating in the 70cm band. Nodes, identified by amateur radio callsigns, can send short text messages to all participants or directly to specific callsigns, functioning as repeaters to extend network reach. The system supports automatic status and position messages, with optional sensor data for WX-Data and Telemetry. MeshCom nodes can be configured as gateways to HAMNET or the internet, enhancing connectivity options. The project emphasizes a self-building and self-healing mesh network architecture, crucial for emergency communication scenarios. Operating frequencies include **433.175 MHz** (EU, USA, Africa), 439.9125 MHz (UK), and 433.925 MHz (Norway). The firmware is compatible with hardware platforms such as ESP32/LoRa modules, RAK-WISBLOCK, and ESP32-DEV4/E22-LoRa, offering a flexible deployment for various amateur radio applications.